Volume control system



Oct. 25, 1932. E. R. HENTSCHEL 1,384,581

vommn CONTROL SYSTEM Filed July 14. 1950 s Sheets-Shet 1 mmvron BY 5ATTbRNEY 1932- E. R. HENTSCHEL VOLUME CONTROL SYSTEM Filed July 14. 19303 Shets-Sheer. 2

' INVENTOR. 6mm $31, Mug/w, BY

+ $5?" RNEY Oct. 25, 1932. E. R. HENTSCHEL'.

VOLUME CUNTROL SYSTEM Filed July 14, 1930 3 Sheets-Sheet 3 JNVENTOR.

ATTORNE:

; Pateilted o'cezs, 1932 UNITED STATES PATENT OFFICE ERNEST R.HENTSCHEL; OF WASHINGTON, DISTRICT OF COLUMBIA; JOHN OLSON, AD-

MINISTRATOR OF SAID ERNEST R. HENTSCHEL, DECEASED, ASSIGNOB TO WIREDRADIO, INC., OF NEW YORK, N. Y., A CORPORATION OF DELAWARE VOLUMECONTROL SYSTEM 4 Application filed July 14, 1930. Serial No. 467,942.

My invention relates broadly to volume control systems and moreparticularly to a circuit arrangement for a broadcast receiver havingmeans for automatically opposing involume of sound reproduced by abroadcast 1 receiver by impressing upon the circuits of theamplification system in the receiver energy in phase operation to theincoming signaling energy for opposing lncrease in amplitude of theincoming signaling energy due to fading effects.

Still another object of my invention is to provide an arrangement ofrectifier circuit associated with the radio frequency amplificationsystem of a broadcast rece ver and energized from a succeeding circuitof the broadcast receiver for impressing upon the preceding circuitcurrent in phase opposition to theincoming signahng current to opposeany tendency of increase in signal amplitude under conditions of fading.

A further object of my invention is to provide a method forautomatically controlling the volume or amplitude of signal ener y in aradio receiver or similar device by tail:-

in ener from some ortion of the radio g my P frequencycircuit when thatenergy exceeds a predetermined value, and feeding this energy into apreceding partqof the circuit in phase opposition to the receivedenergy.

Other and further objects of my invention will be understood from thespecification hereinafter following by reference to the accompanyingdrawings, in which:

Figure 1 illustrates a circuit arran ement for a radiobroadcast'recelyer embodying the principles of my invention; Fig. 2illustrates a modified circuit arrangement for one stage of radiofrequency amplification showing the means for distributing a portionofthe incoming signaling energy to the rectifier control circuit of thevolume control circuit of my invention;'Fig. 3 illustrates anarrangement of detector circuit having means for impressing energyrepresenting the radio frequcncy component. of the received signal uponthe control circuit to the rectifier illustrated in Fig. 1; Fig. 4 showsa further modification of the detector circuit which may be employedaccording to the principles of my invention; Fig. 5 illustrates a methodof connecting the control rectifier for the volume control circuit inparallel with the input circuit of the detector for eiiecting volumecontrol in the receiving system; Fig-6 illustrates a circuit arrangementfor impressing control current from a succeeding portion. of

the receiving circuit to a preceding portion thereof through the shieldgrid circuit of one of the preceding amplifier stages; Fig. 7

illustrates .a modified form ot connection between the control rectifierand the antenna circuit of a radio broadcast receiver; and Fig. 8 showsthe application of my invention to the audio frequency amplifiercircuits of a broadcast receiver. My invention .provides means fordistributing current from a portion of the amplification circuit of aradio broadcast receiver Whenever the amplitude of the incomingsignaling energy exceeds a predetermined value and impressing suchcurrent upon a preceding portion of the amplification circuit in phaseopposition to the phase of the incoming signaling current. Underconditions of fading, the signaling current may rise and fall inamplitude giving undesirable oper- ,ation of the sound reproducing sstem and interfering with the enjoyment o the radio broadcast program.Such fading conditions are apparent in long distance broadcastrec'epti'on' where an incoming program may be i lost in part while otherparts of the program may be received with such amplitude as to beunbearable to the average listener and to'overload the averageloudspeaker. By means of the circuit arrangement of my invention,thevolume of reproduced sound is maintained at substantially constantamplitude. ,I provide a rectifier control circuit which is coupled to aselected portion of the amplificat' n systemior introducing into theamplification system current in phase opposition derived from asucceeding portion of the amplification circuit for opposing the effectsof the incoming signaling energy when ing drawings.

In Fig. 1 is shown one of the arrangements which have been reduced topractice. The

radio receiver is diagrammatically illustrat-' ed as comprising radiofrequency. ampl fier stages 2 and 3, a detector tube 4, and audiofrequency amplifier 60. The input circuit of the radio frequencyamplifier c onnects to antenna system 61 through a coupling systemhavingprimary winding 6 and inductively coupled windings 5 and 7.Conductors 26 represent the busses through which alternating current isconveyed to the filaments of the-tubes, and 25 represents a voltagesupply for the plates and grids of the several tubes, usually arectifier and filter energized from rectified-alternating current. Tube4 is a detector of the plate rectification type. Inductance 13 andcondenser 15 provide a tuned input circuit to the detector 4. Coupled tocoil 13 there is provided a coil 14 which is connected in series withcoil 5, tube 1, and a portion of resistance 29. Coil 5 is coupled toantenna coil 6 and tuned coil 7. Tube 1 is a rectifier. The function ofthe part of resistance 29 included in the circuit is to place a steadynegative potential on the anode 1a of tube 1 so that there will be noflow of electrons from the cathode until the peak radio frequencyvoltage between cathode and,

anode exceeds a predetermined value. This radio frequency voltage isobtained through coil 14 and coil 13, and the voltage at which tube 1 isto pass currentis determined by the amplitude of signal desired in thedetector tube 4. T he desired amplitude is customarily determined bylistening to the output of the receiver through loud speaker 62. Tube 1is biased so that it begins to operate at practically any desiredamplitude of detector input voltage. Before the radio frequencyvoltagereaches this chosen value, there will be no current'in tube 1,coil 5, or coil 14, but when this value is exceeded there will be onepulse of current 'at every cycle. Coil 5 is coupled to coil 6 so thatthe instantaneous values of currents will be in phase opposition, sothat when current begins to flow in coil 5 the energy input to thereceiver is decreased. Condenser 28 i-s placed in the circuit as shownso that the radio frequency current will not need to pass throughresistor 29.

As the current in the antenna 61 is small r compared to that in c011 13any tendency for the antenna current to increase will produce a largeincrease in the bucking current in coil 5, so that the energy input tothe receiver is instantaneously .reduced .to that value at whichrectifier 1 just begins to pass current.

As no energy is drawn frtnn coil 14 When its voltage is lower than thatrequired for .the operation of tube 1, the volume control apparatus doesnot interfere with the reception of weak signals. The coupling betweencoils 14 and 13 is made variable which provides a method of varying theradio frequency voltage applied across tube 1, which gives anothermethod of regulating the amplitude of signal at which the automaticcontrol becomes effective.

There are many methods of tapping sources of this bucking current andmany methods for feeding thisbucking current into another part of thecircuit. Figs. 2 to 8 show several modified circuit arrangements whichmay be used. In each figure only a fragmentary part of the radioreceiving circuit is shown. In all the illustrations, including Fig. 1,the same reference numbers refer to corresponding parts.

In Fig. 2, I have shown a method of tapping energy from the platecircuit of tube 3 in such manner that coil 31 does not appreciably robcoil.13, nor affect its tuning. As the plate resistance of a shield gridtube is high, the external impedance seldom matches it, so this"additional impedance supplied by-coil' 30 and its coupled circuits mayeven increase the efficiency and cause the tube to give betteramplification, which will be beneficial. Coil 31 may be tuned bycondenser 32 if voltage amplification is needed. The two ends of thecoil 31 are connected to tube l and coil 5 asin Fig. 1. 33, representsthe usual Toy-pass condenser. Condenser 32 may be one of a gang ofcondensers, or it may be tuned separately, thereby giving another{)neaps of regulating the voltage on tube num- Fig. 3 shows a method ofusing the radio frequency current in the plate circuit of detector tube4, thus obtaining one more stage of amplification for the volume controlapparatus and eliminating any danger of this apparatus affecting thetuningof the radio fre- 1 quency stages. 34 is a radio frequency chokecoil which forces most of the radio frequency current to flow throughblocking condenser 16 and coil 35 to ground. Coil 36 is coupled to coil35 and its two ends are connected as previously described with referenceto coils 14 and 31 in Figs. land 2. Coil 36 may be tuned with acondenser but thisgreatly increases the effective impedance of coil 35,so it is preferable to operate it as shown because path 16 and 35 mustbe a low impedance path to ground.

Fig. 4 shows a modified form of control circuit wherein the primarywinding 37 of a transformer is directly connected in the plate lead ofthe detector tube 4 between the plate of the tube and the primarywinding 17 of audio frequency transformer 18.

Fig. 5 shows a method of directly tapping the input circuit of detectortube 4 and also another mthod'of feeding the bucking current into theantenna 61. It is not necessary to use thesetwo methods together; anyone of the methods here described of obtaining bucking current may beused with any of the methods for-feeding this current into another partof'thecircuit. In this figure, the energy is taken directly from theends of coil 13. Wire 43 leads from this coil through coil 5 to theanode 1a of two element tube 1. The cathode of this tube is. connectedthrough wire 45, a portion resistance 29, andwire 46 to the other endofcoil 13. Tube 1 and coil 5 act as previously described, except that coil5 is coupled 'to a separate coil 40 in the antenna circuit, and inducesin this coil an E. M. F. which opposes the antenna current. Condenser 42is a by-pass for radio frequency I current. Wires 45 and 46 tap resistor29 at such points that the anode of tube lis at a negative potentialwith respect to the cathode for the reason previously explained. C oil5, instead of being in the position shown, could be inserted at point 56in the wire connected to the cathode of tube 1, and coupled to coil 40asshown.

Fig. 6 illustrates a three clement'rectifier and another method offeeding the bucking current into the circuit. Coil 49 feeds radiofrequency energy into coil 50 which may be tuned by condenser 52 as'shown. The grid is biased by moving contact 'so that no plate currentflows until the radio frequency pulsations in coil 50 exceed apredetermined value. When. this value is exceeded then there are, in theplate circuit, pulsations of current at radio frequency whichmay be usedas previously described for bucking the energy in an preceding partofthe circuit. 51, 53 and 5% represent by-pass condensers, and wire 54taps resistance 29 at the point which gives the proper plate voltage fortube 1a.

There isillustrated here another method offeeding the bucking currentinto the circuit. The current in coil 48 induces an E. M. F. in coil 47which is in the shield grid line of tube 2, thereby causing fluctuationsin the shield grid potential. Coils 48 and 47 are to be so coupled thatthe pulsations of E. M. F. on the shield grid are in such time phase asto directly oppose the pulsations on .the control grid,-and therebyreduce the radio frequency energy in the plate circuit. A small chokecoil 58 may be inserted as shown if it is found that there. isinsuflicient energy supplied the shield grid, so as to prevent loss toground.

This bucking energy may also be intro- Fig. 7 illu strates such aionnection where wires 6 and 63 lead to the .ource' of bucking currentwhiclhflows through resistance 59 setting up van E. M.-F. which opposesthe I antenna E. M. F. Resistance 59 may be replaced by an inductance ora capacity. In-

stead of employing the half wave rectifier shown at 1a, full waverectifier may be used.

My invention is also applicable to the audio frequency amplificationportion of the broadcast receiver as illustrated in Fig. 8. I haveillustrated the detector at 4 associated with the audio frequency poweramplifier tubes 60,and 70. Increases in volumeof reproduced sound in theloud speaker (32 are accompanied by increases in amplitude of the audiofrequency current in the output circuit of power amplifier tube 70,thereby increasing the current through the primary winding (54, whichenergy is inductively transferred to the secondary winding 65 andapplied to the control circuit of rectifier tube 1. The anode circuit ofrectifier tube 1 connects through winding 71 returning to the potentialsource across potentiometer 2S1 returning throughtlie tap (36 to thecathode ful in its operation and while I have shown a number ofembodiments of my invention, I desire that it be understood thatmodifications may be made and that no limitations upon my invention areintended other than are imposed by the scope of the appended claims. a

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. In a signal receivingv system, a multiplicity of electron tubeamplification stages, and means coupling one amplificationstage with apreceding amplification stage for feeding back energy to said precedingamplification stage in phase'opposition to the incoming signaling energyin proportion to a multiplicity of amplification stages, and meanscoupling a portion of one amplification v stage with a portion of apreceding amplification stage for impressing energy there- .on in 180phase displacement. with respect to incoming signaling energy in saidpreceding amplification' stage for regulating the amount of energy insaid signal receiving system.

3. In a signal receiving circuit, an amplification system including amultiplicity of intercoupled electron'tube stages, a circuit extendingbetween a portion of one electron tube stage and a portion of apreceding electron tube stage for transferringcurrent from thesucceeding amplification stage to the preceding amplification stage, andmeans in said circuit for displacing the phase of the current thustransferred with respect to the phase of signaling current in saidpreceding amplification stage, whereby the effects ofincreases inamplitude of incoming'signaling energy are automatically opposed inproportion to the amount of energy received.

4:. A radio broadcast receiver comprising an amplification systemincluding a multiplicity of intercoupled electron tube amplificationstage with the circu t oi a preceding tion of the circuit of oneelectron tube amplification stage with the circuit of a precedlngelectron tube amplification stage for transferring current therebetween,andmean'sfor displacing the phase of the current thus transferred withrespect to the phase of incoming signaling current in said precedingamplification stage for opposing increases in amplitude of the incomingsignaling current for-maintaining the amount of energy in saidamplification stages at a constant value. 7

5. A radio receiving system comprising an amplification system includinga multiplicity of electron tube amplification stages; a circuit couplinga portion of one electron tube amplification stage with a portion of apreceding electron tube amplififcttion stage, and a rectifier disposedin said circuit for rendering effective upon said precedingamplificationstage current impulses opposed in phaseto the phase of theincoming slgnalmg currents in' said preceding electron tube in circuitwith said means, said rectifier having its input -c1rcuit excited byenreceived from said succeeding amer pl cation stage and adapted todeliver current impulses from the output circuit thereof to saidpreceding amplification stage derived from said succeeding amplificationstage and having its output circuit connected to'deliver currentimpulses to said preceding amplificationstagein phase opposition to thephase of the incoming signaling energy, and means for controlling theamplitude of energy delivered from said succeeding amplification stageto the input circuit of said rectifier, whereby increases in signalampli-' tude beyond a predetermined limit introduces opposition efl'ectsbetween the current impulses delivered by said rectifier and theincoming signaling energy.

. In testimony whereof I aflix my signature ERNEST R. HENTSCHEL.

amplification stage for variably controlling thev amplitude of thesignaling energy transferred through said amplification system formaintaining the amplitude 01's signaling energy delivered by the outputof said amplification stages substantially constant.

6. ,A radio broadcast receiver comprising an amplification systemincluding a multiplicity of intercoupled electron tube amplificationstages, means intercoupling a portion of the circuit of one electrontube amplification stage with the'pircuit of a preceding electron tubeamplification stage for transferrin current tiierebetween, and arectifier dispose

